1. Field of the Invention
The present invention relates to a hydrazone dye having a novel structure, and relates to a dye used in recording materials for thermal transfer recording, ink jet recording and the like, and to a colorant (composition) for use in a filter or the like.
2. Description of the Related Art
Azo dyes are dyes which are used the most; they account for more than half of the dyes which are used.
There are many publications about azo dyes. Representative among them are Color Chemistry (Heinrich Zollinger, Weinheim, New York, Basel, Cambridge 1987), Synthetic Dyes (Gosei Senryou) (Hiroshi Horiguchi, Sankyo Shuppan KK, 1970), and the like. Details are described in the chapters on azo dyes and azo pigments.
An azo dye is generally defined as being a structure in which a carbon having an sp.sup.2 hybrid orbital is bonded to each of the both ends of an azo group (--N.dbd.N--).
For example, the compound azobenzene represented by the following formula falls into the category of azo dyes. ##STR2##
When azobenzene has a dissociated group, a tautomer is generated depending on the position of the dissociated group. For example, in an azobenzene in which --OH is substituted at the position next to the azo group, the following tautomer is generated. azo structure hydrazone structure ##STR3##
A detailed discussion relating to tautomers of azobenzene can be und on pages 133 through 137 of the aforementioned Color Chemistry.
In order to improve the hue such as making the absorption of the dye sharper or the like, it is preferable to lean toward either an azo structure or a hydrazone structure. Or, structures that do not produce tautomers are preferable. However, there has still not been developed a cyan color forming azo dye resulting in a good hue.